Climatic classification and ordination of the Spanish Sistema Central: relationships with potential vegetation

Comparisons among European, Japanese and North-American temperate deciduous woody floras revealed that there is no difference in shade-tolerance or in successional position between the compound- and simple-leaved species. Given that the compound-leaved species usually have greater biomass investments in non-productive throwaway supporting structures, it remained unclear how they could be as shade-tolerant as the simple-leaved analogues. To find out the role of the variability in leaf structure and composition in shade-tolerance of these species, foliar morphology and chemistry were analysed in 15 Estonian temperate compound-leaved deciduous woody taxa.Both foliar morphological and chemical parameters influenced the fractional investment of foliar biomass in petioles. The proportion of leaf biomass in petioles was independent of leaf size, but it increased with increasing leaflet number per leaf, suggesting that spacing rather than support requirements determined the biomass investment in petioles. The leaves with greater nitrogen concentrations also had larger foliar biomass investments in petioles. The latter effect possibly resulted from a greater water demand of functionally more active protein-rich leaves. Though the proportion of leaf biomass invested in petioles was high (for the whole material on average 15.9±0.4%), petioles were considerably cheaper to construct in terms of mineral nutrients than leaflets. e.g., petioles contained on average only 5.55±0.14% of total leaf nitrogen. Since in many cases the availability of mineral nutrients such as nitrogen rather than organic carbon sets limits to total leaf biomass on the plant, I suggested, contrary to previous claims, that the costs for foliage formation should not necessarily be different between compound- and simple-leaved species. Compound-leaved species also fit the basic relationships previously observed in simple-leaved analogues. Leaf size increased and leaf dry mass per area (LMA) decreased with increasing shade-tolerance. Thus, more shade-tolerant species construct a more effective foliar display for light interception at low irradiance with similar biomass investment in leaves. Species shade-tolerance was independent of biomass investment in petioles. However, due to the genotypic plasticity in LMA, more shade-tolerant species supported more foliar area at a constant leaf biomass investment in petioles.     

Inter‐specific Variation in Foliar Nutrients and Resorption of Nine Canopy‐tree Species in a Secondary Neotropical Rain Forest

The influence of environmental gradients on the foliar nutrient economy of forests has been well documented; however, we have little understanding of what drives variability among individuals within a single forest stand, especially tropical forests. We evaluated inter‐ and intra‐specific variation in nutrient resorption, foliar nutrient concentrations and physical leaf traits of nine canopy tree species within a 1‐ha secondary tropical rain forest in northeastern Costa Rica. Both nitrogen (N) and phosphorus (P) resorption efficiency (RE) and proficiency of the nine tree species varied significantly among species, but not within. Both N and P RE were significantly negatively related to leaf specific strength. Green leaf N and P concentrations were strongly negatively related to leaf mass per area, and senesced leaf nutrient concentrations were significantly positively related to green leaf nutrient concentrations. This study reveals a strong influence of physical leaf traits on foliar nutrient and resorption traits of co‐occurring species in a secondary wet tropical forest stand.     

Patterns of plant sexual systems in subtropical evergreen broad-leaved forests in Ailao Mountains,SW China

Aims Sexual systems influence many components of the ecology and evolution of plant populations and have rarely been documented in subtropical evergreen broad-leaved forests (SEBLF). Here we report frequency distribution and ecological correlates of plant sexual systems in SEBLF at Ailao Mountains, and compare our results with that of tropical and cool temperate forests.Methods We examine the sexual systems of 703 species of woody angiosperms belonging to 103 families and 296 genera based on a comprehensive survey of SEBLF at Ailao Mountains Natural Reserve. Information of plant sexual systems and ecological traits were mainly based on published literatures and specimens as well as our field observations. The associations between plant sexual system and ecological traits were assessed with chi-square tests.Important findings Among these species, 60.2% were hermaphroditic, 15.8% were monoecious and 24.0% were dioecious. The percentage of dioecious sexual system among tree species (22.2%) in SEBLF was comparable to those of tropical tree floras, but much higher than those of temperate forests at North America. The percentage of monoecious sexual system among tree species (30.1%) in SEBLF was higher than that of tropical tree floras, but much lower than those of temperate forests at North America. Monoecy was significantly associated with the tree growth form and was relatively common in temperate genera. Dioecy was significantly associated with fleshy fruits and monoecy was significantly associated with dry fruit type in SEBLF. The high percentage of diclinous sexual systems (monoecy and dioecy) in SEBLF may be associated with the origin of the flora and the prevalence of relatively small inconspicuous flowers of the forests in the Oriental Region.     

A galloylated cyanogenic glycoside from the Australian endemic rainforest tree Elaeocarpus sericopetalus (Elaeocarpaceae)

A cyanogenic glycoside - 6'-O-galloylsambunigrin - has been isolated from the foliage of the Australian tropical rainforest tree species Elaeocarpus sericopetalus F. Muell. (Elaeocarpaceae). This is the first formal characterisation of a cyanogenic constituent in the Elaeocarpaceae family, and only the second in the order Malvales. 6'-O-galloylsambunigrin was identified as the principal glycoside, accounting for 91% of total cyanogen in a leaf methanol extract. Preliminary analyses indicated that the remaining cyanogen content may comprise small quantities of sambunigrin, as well as di- and tri-gallates of sambunigrin. E. sericopetalus was found to have foliar concentrations of cyanogenic glycosides among the highest reported for tree leaves, up to 5.2 mg CN g(-1) dry wt.     

Neotropical seasonally dry forests and Quaternary vegetation changes

Seasonally dry tropical forests have been largely ignored in discussions of vegetation changes during the Quaternary. We distinguish dry forests, which are essentially tree‐dominated ecosystems, from open savannas that have a xeromorphic fire‐tolerant, grass layer and grow on dystrophic, acid soils. Seasonally dry tropical forests grow on fertile soils, usually have a closed canopy, have woody floras dominated by the Leguminosae and Bignoniaceae and a sparse ground flora with few grasses. They occur in disjunct areas throughout the Neotropics. The Chaco forests of central South America experience regular annual frosts, and are considered a subtropical extension of temperate vegetation formations. At least 104 plant species from a wide range of families are each found in two or more of the isolated areas of seasonally dry tropical forest scattered across the Neotropics, and these repeated patterns of distribution suggest a more widespread expanse of this vegetation, presumably in drier and cooler periods of the Pleistocene. We propose a new vegetation model for some areas of the Ice‐Age Amazon: a type of seasonally dry tropical forest, with rain forest and montane taxa largely confined to gallery forest. This model is consistent with the distributions of contemporary seasonally dry tropical forest species in Amazonia and existing palynological data. The hypothesis of vicariance of a wider historical area of seasonally dry tropical forests could be tested using a cladistic biogeographic approach focusing on plant genera that have species showing high levels of endemicity in the different areas of these forests.     

Do leaf margins of the temperate forest flora of southern South America reflect a warmer past?

Aim   Our aims were: (1) to characterize the linear relationship between the proportion of woody dicotyledonous species with entire-margined leaves ( E ) and mean annual temperature (MAT) from a southern temperate flora that still harbours many lineages that originated under warmer climates; (2) to compare this relationship with those developed from floras of different regions of the world; and (3) to contrast temperature predictions based on leaf margins of the native southern flora versus the naturalized alien flora, mostly of boreal origin.
Location   The temperate forest of southern South America (TFSA).
Methods   At each 1° latitudinal band, we estimated E based on species latitudinal ranges and MAT from both an isotherm map and a global temperature grid. We also calculated E from five local floras located between 40 and 43° S, and from the naturalized alien flora of Nahuel Huapi National Park in southern Argentina.
Results   We found a close relationship between E and MAT for the TFSA. Equations developed from floras of the Northern Hemisphere overestimated extant temperatures of this biome by 6–10 °C at both geographical and local spatial scales. On the other hand, MAT predictions from leaf margins of the alien flora were similar to the actual MAT. A published regression between E and MAT from tropical South America was remarkably similar to the one we estimated from the TFSA. This tropical equation predicted accurately the temperatures observed for this temperate biome based on leaf margins of the native flora.
Main conclusions   Despite massive plant extinction due to environmental cooling and biogeographical isolation during the Tertiary, leaf-margin analysis reveals that the flora of the TFSA still reflects its original development under the warmer conditions of western Gondwana and its past connections with low-latitude forest floras of tropical South America.     

A comparative study of metal levels in leaves of some Al-accumulating Rubiaceae

Concentrations of Al, Si, Fe, Mn, Cu and Ca were analysed in leaves of ten Rubiaceae species, most of which are Al accumulators, and these were compared with concentrations in one species of Melastomataceae. Quantitative data confirmed the distribution of Al accumulation as previously determined by semi-quantitative tests, and suggest that there is an apparent congruency between the shoot Al concentration and the number of accumulators within a certain genus or tribe. Al accumulators within the Rubiaceae are most characteristic of the Rubioideae subfamily, although a second origin is likely in at least a few members of the tribes Vanguerieae and Alberteae. While the leaf Si concentration in Melastomata malabathricum L. (Melastomataceae) was negligible, all Rubiaceae studied showed relatively high Si levels (mostly >3000 mg kg(-1)). It is hypothesized that an Al-Si complex is formed in the shoot tissues of Al-accumulating Rubiaceae and that this may contribute to Al detoxification. However, the Si : Al mole ratio tended to differ widely among species. There was no significant correlation between Al and the other metals analysed. A remarkably high Mn concentration was found in Coptosapelta olaciformis Elm.     

Ingestion and assimilation of leaf litter in some tropical millipedes

Ingestion and assimilation rates in six species of tropical millipede (Diplopoda: Spirostreptidae) from southern Africa are estimated for the first time and were found to vary both within and between species. A proportion of this variability was attributable to variation in body size effects as individuals ranged from 0.2 to 2.9 g dry mass. Mean ingestion rates for each species were 17,30, 34.32 and 75 mg dry leaf litter per day (7.6 to 2.6% of body mass). Within species, ingestion rates explained between 35 and 53% of the variation in assimilation. Large size did not necessarily enhance assimilation efficiencies, which were between 7 and 26%) and comparable to assimilation efficiencies reported for temperate species, but did result in greater absolute ingestion and assimilation of organic material per individual.     

The incidence and implications of clouds for cloud forest plant water relations

Although clouds are the most recognisable and defining feature of tropical montane cloud forests, little research has focussed on how clouds affect plant functioning. We used satellite and ground‐based observations to study cloud and leaf wetting patterns in contrasting tropical montane and pre‐montane cloud forests. We then studied the consequences of leaf wetting for the direct uptake of water accumulated on leaf surfaces into the leaves themselves. During the dry season, the montane forest experienced higher precipitation, cloud cover and leaf wetting events of longer duration than the pre‐montane forest. Leaf wetting events resulted in foliar water uptake in all species studied. The capacity for foliar water uptake differed significantly between the montane and pre‐montane forest plant communities, as well as among species within a forest. Our results indicate that foliar water uptake is common in these forest plants and improves plant water status during the dry season.     

DA-6对秋季草莓叶片光合速率和植株生长的影响

以‘法国3号’草莓为材料,研究了秋季叶面喷施10、20和30 mg.L-1的DA-6处理对草莓幼苗叶片光合作用、活性氧代谢和植株生长的影响.结果表明:叶面喷施20和30 mg.L-1的DA-6处理使叶片净光合速率分别提高了17.5%和20.6%,并显著提高了叶绿素a、b含量及SOD、CAT酶活性,同时降低了MDA和活性氧含量.20和30 mg.L-1的DA-6处理显著增加了草莓平均单叶干质量,极显著增加了草莓茎和根系干质量,根冠比分别增加了29.9%和29.3%.表明秋季施用一定浓度的DA-6有利于草莓幼苗植株生长.     

Silicon in tropical forests: large variation across soils and leaves suggests ecological significance

Silicon (Si) has a variety of functions in plants, including alleviation of drought and light stress, defense against herbivores and pathogens, and improving plant nutrition. However, for tropical forests our knowledge about the role of silicon and its variation in soils and plants remains limited. To advance our insights into the potential role of Si in tropical forest ecology, we combined observational and experimental approaches to assess (i) variation in soluble and amorphous Si concentrations in tropical forest soils at the local and regional scale, and their relation to soil weathering stage, soil chemistry, and rainfall, (ii) variation of foliar Si concentrations across more than 30 co-occurring woody species, and (iii) intra-specific variation of foliar Si across sites and foliar habits (sun and shade). We found considerable (27-fold) variation in soluble Si (extracted in 0.01 M CaCl₂) across soils, which reflected soil weathering stage and chemistry, but not rainfall. Foliar Si also varied markedly across species, both in naturally occurring trees and in a common garden experiment, with 39% of the most abundant species being classified as Si accumulators. Within species, foliar Si varied among sites and foliar habits, but relationships were inconsistent across species. The marked variability of Si concentrations in soils and leaves indicates that Si is likely to play an important yet underappreciated role for a variety of ecological processes in tropical forests.     

Leaf nonstructural carbohydrate concentrations of understory woody species regulated by soil phosphorus availability in a tropical forest

Leaf soluble sugars and starch are important components of nonstructural carbohydrates (NSCs), which are crucial for plant growth, development, and reproduction. Although there is a large body of research focusing on the regulation of plant NSC (soluble sugars and starch) concentrations, the response of foliar NSC concentrations to continuous nitrogen (N) and phosphorus (P) addition is still unclear, especially in tropical forests. Here, we used a long‐term manipulative field experiment to investigate the response of leaf NSC concentrations to continuous N and P addition (3‐, 5‐, and 8‐year fertilization) in a tropical forest in southern China. We found significant species‐specific variation in leaf NSC concentrations in this tropical forest. Phosphorus addition dramatically decreased both leaf soluble sugar and starch concentrations, while N addition had no significant effects on leaf soluble sugar and starch concentrations. These results suggest that, in plants growing in P‐limiting tropical soil, leaf NSC concentrations are regulated by soil P availability rather than N availability. Moreover, the negative relationships between NSC concentrations and leaf mass per area (LMA) revealed that NSCs could supply excess carbon (C) for leaf expansion under P addition. This was further supported by the increased structural P fraction after P fertilization in our previous study at the same site. We conclude that soil P availability strongly regulates leaf starch and soluble sugar concentrations in the tropical tree species included in this study. The response of leaf NSC concentrations to long‐term N and P addition can reflect the close relationships between plant C dynamics and soil nutrient availability in tropical forests. Maintaining relatively higher leaf NSC concentrations in tropical plants can be a potential mechanism for adapting to P‐deficient conditions.     

中国4种典型森林中常见乔木叶片的非结构性碳水化合物研究

植物叶片的非结构性碳水化合物(non-structural carbohydrates,NSC)不仅为植物的代谢过程提供重要能量,还能一定程度上反映植物对外界环境的适应策略。以温带针阔混交林(长白山)、温带阔叶林(东灵山)、亚热带常绿阔叶林(神农架)和热带雨林(尖峰岭)4种森林类型的树种为研究对象,利用蒽酮比色法测定了163种常见乔木叶片可溶性糖、淀粉和NSC(可溶性糖+淀粉)含量,探讨了不同森林类型植物叶片NSC的差异及其地带性变化规律。结果显示：（1）从森林类型上看,植物叶片NSC含量从北到南递减,即温带针阔混交林(170.79 mg/g)>温带阔叶林(100.27 mg/g)>亚热带常绿阔叶林(91.24 mg/g)>热带雨林(80.13 mg/g)。（2）从生活型上看,无论是落叶树还是阔叶树,其叶片可溶性糖、淀粉和NSC含量均表现为：温带针阔混交林>温带阔叶林>亚热带常绿阔叶林>热带雨林;北方森林叶片可溶性糖、淀粉和NSC含量均表现为落叶树种>常绿树种,或阔叶树种>针叶树种。（3）森林植物叶片NSC含量、可溶性糖与淀粉含量比值与年均温和年均降水量均呈显著负相关。研究表明,森林植物叶片可溶性糖、淀粉和NSC含量以及可溶性糖与淀粉含量比值均具有明显的从北到南递减的地带性规律;其NSC含量以及可溶性糖与淀粉含量比值与温度和水分均呈显著负相关的变化规律可能是植物对外界环境适应的重要机制之一。该研究结果不仅为阐明中国主要森林树种碳代谢和生长适应对策提供了数据基础,而且为理解区域尺度森林植被对未来气候变化的响应机理提供新的视角。     

CSR analysis of plant functional types in highly diverse tropical grasslands of harsh environments

The classification of plant species according to the CSR ecological strategy scheme has been proposed as a common language that allows comparison among species, communities, and floras. Although several studies on European continent have demonstrated a consistent association between CSR strategies and key ecosystem processes, studies of this type are still lacking in other ecoregions worldwide. For the first time, the CSR strategy scheme is applied in a tropical plant community. In a Brazilian mountain grassland ecosystem characterized by both high biodiversity and environmental stress, we sampled various functional traits of 48 herbaceous species in stony and sandy grasslands, and evaluated the relationship between CSR strategies and functional traits with several environmental parameters. The extremely infertile soils in the two studied habitats may have acted as a major environmental filter leading to a clear predominance of the stress-tolerant strategy in both communities. However, fine-scale environmental differences between the two communities resulted in the filtering of distinct functional trait values. The sites with coarser soil texture, lower percentage of plant cover and (paradoxically) higher mineral nutrient concentrations favored plants with narrower leaves, higher stress tolerance, lower competitiveness, and higher sclerophylly (i.e., lower specific leaf area and higher leaf dry matter content). The comparison between the functional character of stony and sandy communities evidenced the influence of soil texture and water availability in the environmental filtering. This study highlighted the validity of the CSR classification outside the temperate region where it was originally developed and corroborated.     

Leaf structural and photosynthetic characteristics,and biomass allocation to foliage in relation to foliar nitrogen content and tree size in three Betula species

Young trees 0.03-1.7 m high of three coexisting Betula species were investigated in four sites of varying soil fertility, but all in full daylight, to separate nutrient and plant size controls on leaf dry mass per unit area (MA), light-saturated foliar photosynthetic electron transport rate (J) and the fraction of plant biomass in foliage (F(L)). Because the site effect was generally non-significant in the analyses of variance with foliar nitrogen content per unit dry mass (N(M)) as a covariate, N(M) was used as an explaining variable of leaf structural and physiological characteristics. Average leaf area (S) and dry mass per leaf scaled positively with N(M) and total tree height (H) in all species. Leaf dry mass per unit area also increased with increasing H, but decreased with increasing N(M), whereas the effects were species-specific. Increases in plant size led to a lower and increases in N(M) to a greater FL and total plant foliar area per unit plant biomass (LAR). Thus, the self-shading probably increased with increasing N(M) and decreased with increasing H. Nevertheless, the whole-plant average M(A), as well as M(A) values of topmost fully exposed leaves, correlated with N(M) and H in a similar manner, indicating that scaling of MA with N(M) and H did not necessarily result from the modified degree of within-plant shading. The rate of photosynthetic electron transport per unit dry mass (J(M)) scaled positively with N(M), but decreased with increasing H and M(A). Thus, increases in M(A) with tree height and decreasing nitrogen content not only resulted in a lower plant foliar area (LAR = F(L)/M(A)), but also led to lower physiological activity of unit foliar biomass. The leaf parameters (J(M), N(M) and M(A)) varied threefold, but the whole-plant characteristic FL varied 20-fold and LAR 30-fold, indicating that the biomass allocation was more plastically adjusted to different plant internal nitrogen contents and to tree height than the foliar variables. Our results demonstrate that: (1) tree height and N(M) may independently control foliar structure and physiology, and have an even greater impact on biomass allocation; and (2) the modified within-plant light availabilities alone do not explain the observed patterns. Although there were interspecific differences with respect to the statistical significance of the relationships, all species generally fit common regressions. However, these differences were consistent, and suggested that more competitive species with inherently larger growth rates also more plastically respond to N and H.     

中国西南干旱河谷植被的区系地理成分与空间分异

根据对云南、四川、甘肃三省九条主要河流干旱河谷的植物群落调查数据, 对我国西南干旱河谷维管束植物区系的科、属分布区类型进行划分, 并分析其地理分布格局。结果表明: (1)西南干旱河谷区的植物区系地理成分复杂, 联系广泛, 共包含11个科级和15个属级分布区类型; 总体上, 科、属两级热带/温带成分比例分别为3.06和1.77, 显示了强烈的热带区系亲缘及温带区系的后期影响; 与地中海-西亚至中亚植物区系存在一定联系; 其东亚成分和中国特有成分比例低于亚热带区系平均水平, 且中国-喜马拉雅成分比例高于中国-日本成分。(2)从西南向东北方向, 植物区系的热带性质逐渐减弱, 温带性质逐渐增强; 科、属水平区系成分与古地中海-中亚区系的相似性逐渐增强; 东亚和中国特有成分比例增加; 南盘江与元江的干旱河谷植物区系之间存在中国-日本和中国-喜马拉雅成分的分界线。(3)根据干旱河谷植物属区系成分的比例构成将怒江、澜沧江和元江与其他流域分开, 显示了长江溯源侵蚀和水系合并对西南诸河流植物区系发育的影响。     

Leaf Water Repellency as an Adaptation to Tropical Montane Cloud Forest Environments

Adaptations that reduce water retention on leaf surfaces may increase photosynthetic capacity of cloud forests because carbon dioxide diffuses slower in water than air. Leaf water repellency was examined in three distinct ecosystems to test the hypothesis that tropical montane cloud forest species have a higher degree of leaf water repellency than species from tropical dry forests and species from temperate foothills-grassland vegetation. Leaf water repellency was measured by calculating the contact angle of the leaf surface and the line tangent to a water droplet through the point of contact on the adaxial and the abaxial surface. Leaf water repellency was significantly different between the three study areas. The hypothesis that leaf water repellency is higher in cloud forest species than tropical dry forests and temperate foothills-grassland vegetation was not confirmed in this study. Leaf water repellency was lower for cloud forest species (adaxial surface = 50.8°; abaxial surface = 82.9°) than tropical dry forest species (adaxial surface = 74.5°; abaxial surface = 87.3°) and temperate foothills-grassland species (adaxial surface = 77.6°; abaxial surface = 95.8°). The low values of leaf water repellency in cloud forest species may be influenced by presence of epiphylls and loss of epicuticular wax on the leaf surfaces.     

Traits and ecological strategies of Australian tropical and temperate climbing plants

Aim Understanding large scale patterns in trait variation in climbing plants (lianas, vines, scramblers, twiners) is important for the development of a stronger theoretical understanding of climbing plant ecology and for more applied issues such as prediction of community assembly under changing climatic conditions. We compared values of five key functional traits for 388 species of climbing plant from tropical and temperate regions of Australia to quantify variation between these two biogeographic regions. Location Australia. Methods Data on dispersal mode, growth habit, leaf form, leaf size and seed mass were compiled from field measurements and published sources. Comparative analyses were performed in three ways: (1) across species where each species was treated as an independent data point, (2) using evolutionary divergence analyses for each trait, and (3) in multidimensional space using a matrix of similarities between species. Results Tropical climbing plants had 22‐fold greater seed mass and four times greater leaf size than did temperate species. Tropical climbers were more likely to be woody (63%) than were temperate species (40%). Surprisingly we found a similar proportion of animal‐dispersed seeds in the two regions, although we expected animal‐dispersed seeds to be more prevalent in the tropics. We also found similar proportions of simple‐ and compound‐leaved species between the two regions. All of our findings were consistent between cross‐species and phylogenetic analyses indicating that patterns in present‐day species are reflected in the evolutionary history of Australian climbers. Multivariate analyses suggested that there is a spectrum of variation among climbing plants, with tropical species having greater seed mass, leaf size and woody growth compared with temperate climbing plant species. Main conclusions Tropical and temperate climbers of Australia exhibit a mixture of similar and contrasting traits and ecological strategies. Understanding strategy variation along latitudinal gradients will be particularly informative for predicting ecosystem and community structure with climate change.     

Halving sunlight reveals no carbon limitation of aboveground biomass production in alpine grassland

In temperate alpine environments, the short growing season, low temperature and a slow nutrient cycle may restrict plant growth more than carbon (C) assimilation does. To test whether C is a limiting resource, we applied a shade gradient from ambient light to 44% (maximum shade) of incident photon flux density (PFD) in late successional, Carex curvula‐dominated alpine grassland at 2,580 m elevation in the Swiss central Alps for 3 years (2014–2016). Total aboveground biomass did not significantly decrease under reduced PFD, with a confidence interval ranging from +4% to ?15% biomass in maximum shade. Belowground biomass, of which more than 80% were fine roots, was significantly reduced by a mean of 17.9 ± 4.6% (±SE), corresponding to 228 g/m², in maximum shade in 2015 and 2016. This suggests reduced investments into water and nutrient acquisition according to the functional equilibrium concept. Specific leaf area (SLA) and maximum leaf length of the most abundant species increased with decreasing PFD. Foliar concentration of nonstructural carbohydrates (NSC) was reduced by 12.5 ± 4.3% under maximum shade (mean of eight tested species), while NSC concentration of belowground storage organs were unchanged in the four most abundant forbs. Furthermore, maximum shade lowered foliar δ¹³C by 1.56 ± 0.35‰ and increased foliar nitrogen concentrations per unit dry mass by 18.8 ± 4.1% across six species in 2015. However, based on unit leaf area, N concentrations were lower in shade (effect of higher SLA). Thus, while we found typical morphological and physiological plant responses to lower light, shading did not considerably affect seasonal aboveground biomass production of this alpine plant community within a broad range of PFD. This suggests that C is not a growth‐limiting resource, matching the unresponsiveness to in situ CO₂ enrichment previously reported for this type of grassland.     

Paleoclimatic Analysis of Paleogene Flora in Yilan County,Heilongjiang

Plant fossils were collected from the sand-shale above the lower coal seam and the upper oil shale above the upper coal seam in the Yilan coal mine, Heilongjiang. The floras contained 2 species of pteridophytes, 10 species of gymnosperms and over 58 species of angiosperms assigned to 46 genera and 34 families. The fossils were divided into two floras, one of which was in lower sand-shale beds, with the age assigned to the Eocene, and the other was in the upper part of oil shales considered to belong to the Oligocene. The floras were complicated in composition and rich in species, and were studied by means of floristic analysis, foliar architectural and physiognomical analysis. The Eocene flora consisted of many evergreen broad-leaved species, which indicated that the flora belonged to north subtropical evergreen broad-leaved forest or subtropical coniferous and broad-leaved mixed forest. The foliar physiognomical analysis of the floristic composition showed that the species with entire leaf margines made up 38.3 percent of the total. The climate in the Eocene was estimated by means of climatic nomogram as follow: The mean annual temperature was 13.2 ℃ and annual temperature deviancy was 20℃. In the Oligocene flora, deciduous broadleaved trees were dominant, which indicated that the vegetation was of temperate deciduous broad-leaved forest or warm temperate coniferous and deciduous broad-leaved mixed forest. The species with entire leaf margines were 30. 8 percent with an estimated mean annual temperature of 11 ℃ and mean annual temperature deviancy of 25 ℃. The floristic aspect and climate in the Paleogene of Yilan region were very different from the present ones.